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Analog-Digital Hybrid Modulation

for improved efficiency over Broadband Wireless Systems

This paper seeks to present ways to eliminate the inherent quantization noise component

in digital communications, instead of conventionally making it minimal. It deals with a

new concept of signaling called the Signal Code Modulation (SCM) Technique. The

primary analog signal is represented by: a sample which is quantized and encoded

digitally, and an analog component, which is a function of the quantization component of

the digital sample. The advantages of such a system are two sided offering advantages of

both analog and digital signaling. The presence of the analog residual allows for the

system performance to improve when excess channel SNR is available. The digital

component provides increased SNR and makes it possible for coding to be employed to

achieve near error-free transmission.

we introduce the concept of Signal Code Modulation (SCM) which utilizes both the

analog, as well as, digital modulation techniques. The primary analog input signal is

sampled at the appropriate rate and quantized. The digital samples are denoted by

symbols D. The resulting D symbols are then transmitted using digital transmission

techniques (like QAM) optimized for that channel. Those D symbols represent N bits per

analog input sample.

The quantization residual, which is not left behind, is transmitted over the noisy channel

as an analog symbol A, corresponding to the digital symbol D,To produce the

quantization error A, the quantized data is converted back into analog form and

subtracted from the original analog input signal. This symbol A, for noise immunity, is

amplified by a gain of 2N (or any proportional factor that will optimize the voltage swing

of the signal with that of the channel).

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